It is known that during the tire production cycle, and more generally when many articles of elastomer material are to be manufactured, a molding and vulcanization step is provided in which the article of manufacture initially in a raw state, is closed into a mold and submitted to a combined pressure and temperature action by effect of which the article of manufacture is shaped according to the desired geometrical configuration and definitively consolidated into this geometrical configuration and also into its physico-molecular structure, as a result of a molecular cross-linking in the elastomer material caused by high temperature.
However, during each vulcanization cycle the tire deposits a very thin rubber layer over the mold surfaces with which it comes into contact. The thickness of this layer becomes increasingly greater as the vulcanization cycles are repeated. Therefore, in the long run, it can reach such values that the aesthetical features of the finished tire are impaired to an unacceptable level and the air vents necessarily provided in the mold walls for ensuring evacuation of the air entrapped between the surface of the article of manufacture to be vulcanized and that of the mold are partly or completely obstructed. Submitting the mold to a careful cleaning action after a certain number of vulcanization cycles becomes therefore necessary.
These cleaning operations presently provide that the mold should be removed from the vulcanization press to be submitted to sandblasting and/or washing operations by means of particular chemical agents within appropriate machines.
When dismantling of the mold occurs, the press shall remain inactive over a certain period of time which may have a duration of eight hours, that is a whole work shift, in that a lapse of time is first required for enabling cooling of the mold, followed by another period of time needed by manpower for dismantling of the mold itself, in turn followed by a further period of time for mounting of another mold and pre-heating of the same until the operating temperature is achieved.
These periods can be reduced, even to a great extent, if automatic systems for quick mold release and devices for mold pre-heating are utilized, but in any case dismantling of the mold from the press is required. This does not represent a drawback when the mold needs to be disassembled in any case to be replaced with another mold of different size and/or tread pattern. However, it is a very onerous operation when the vulcanization cycle must go on with the same tire pattern. In this case the expensive "machine stoppage" to which the press is submitted can be avoided only when another identical mold is available for being mounted in place of the one sent to cleaning. To have such an identical mold available requires a mold pool (inventory) having excess pieces with respect to the real production necessities (keeping such excess pieces in stock is an expensive solution to the problem).